An E&E Special Report

WEATHER:

Do we need a better yardstick to measure severe droughts?

Tiffany Stecker, E&E reporter

ClimateWire: Friday, May 10, 2013

After more than a decade, the U.S. Drought Monitor might be due for a tuneup.

As Illinois' State Climatologist Jim Angel puts it, it's like the scene in the 1984 parody of hard rock documentaries "This Is Spinal Tap" in which heavy metal guitarist Nigel Tufnel shows off his amplifiers with volume knobs that go up to 11.

Tufnel's amplifiers, he brags to the filmmaker in the spoof, give his guitars that ear-splitting "extra push off the cliff" compared with traditional amps that only reach 10.

Ryan Gronewold, a district coordinator for the Army Corps of Engineers, measures the decline of the Rio Grande River. For three straight years, snowpack that feeds the river has dropped by 50 percent. Photo by Ronnie Schelby, courtesy of the Army Corps.

Angel sees this as an analogy for the Drought Monitor, the weekly map of drought-afflicted areas in the country. After a long, widespread U.S. drought that has drawn comparisons to the 1930s Dust Bowl, do the makers of the map need to crank up the magnitude of the worst-hit spots from D4 -- the current designation for exceptional drought -- and create a D5?

"We know that the climate we have now isn't the climate from 1965," said Michael Brewer, one of the authors of the Drought Monitor and a scientist at the National Climatic Data Center in Asheville, N.C. That was the year the Palmer Drought Severity Index was introduced, and it is used as the primary drought indicator today.

It's very possible that D4 won't be an accurate measure for the most severe drought in the future, said Angel, who referenced the "Spinal Tap" scene at the U.S. Drought Monitor Forum last month in West Palm Beach, Fla. What was once a D4 event is milder than what exceptional drought looks like today. As climate change makes these things more uncertain, the authors of the Drought Monitor are asking themselves whether, and how, to adapt.

A mosaic pieced together by volunteers

Since 1999, the Drought Monitor has not missed a week. The massive amount of information is assessed and written by 11 authors, who each undertake two two-week volunteer stints at writing the monitor per year on top of their jobs at the Agriculture Department, the National Oceanic and Atmospheric Administration, the National Drought Mitigation Center, and other groups that measure atmospheric changes.

About 350 participants respond from across the country to verify what the authors see in satellite images.

The cut-off date for the Drought Monitor is 8 a.m. Eastern time Tuesday. What follows is a frenzy of hundreds of emails, conference calls, individual phone calls and at least three drafts before the map is posted on the Drought Mitigation Center's website at 8:30 a.m. every Thursday. Phone calls and emails come streaming in from journalists, climatologists and citizens. Most are calling or writing to complain.

"[People think] we try to show things better or worse than they are because we have an agenda, [for] job stability," said Brian Fuchs, director of the National Drought Mitigation Center.

"Then we tell them, well, we have no budget," he added, laughing.

The authors use a blend of indicators -- precipitation, vegetation, snowmelt, soil moisture, stream flows and reservoir levels, among others. The Drought Monitor has shaped policy, from the 2008 farm bill to state drought plans. Today, it receives about 3.5 million page views per week.

It's raining data

It's a far cry from the early days and, at times, can be overwhelming. There has been an enormous rise in the amount of data to process each week in order to get a map out Thursday morning, Fuchs said. Nevertheless, there's plenty of room to grow.

"Do we reach a threshold where it's just data overload and we can't physically do that anymore? I don't think we're there yet, we're probably not even approaching that," he said. "We have a lot of tools at our disposal."

Better computing capabilities have fine-tuned the scale of the map. It used to take rainfall from 15 to 20 counties to draw an accurate distribution of drought levels. Now it takes only two or three, Fuchs said.

But much work remains to be done. Aside from climate change, the Drought Monitor can sometimes lose its relevance over certain parts of the country. Take the Big Cypress National Preserve in Florida. The Drought Monitor depends on a specific index to measure the risk of wildfire for the United States. But under the giant cypress trees, it is simply not an accurate measure of wildfire, said Bob Sobczak, a hydrologist at Big Cypress in the Everglades.

In the dense, swamplike preserve, where the peaty soil is underwater most of the year and the annual rainfall patterns are different than in the north, an atmospheric drought based on rainfall doesn't factor in the time water stays in the soils.

"I think it's an incredibly useful tool, but it's a question of how we can add layers to that," Sobczak said. A water supplier in Florida that relies on conditions in the Everglades to water Miami or Tampa might have its eye on the Drought Monitor and, at the same time, at groundwater levels.

Wanted: a better grasp of a growing problem

Adding layers to the Drought Monitor could also alleviate some of the hopelessness associated with drought, turning an act of fate into an event that can be managed, Sobczak said. California is an example where lack of rainfall and soil moisture doesn't necessarily translate into massive cracks in the earth or brown lawns.

The state's investments in irrigation and water management have allowed cities like Los Angeles to feel fewer drought impacts, said Brewer of the Drought Monitor.

The goal of the Drought Monitor is to continue to perfect its measurements, Fuchs said. The area that has developed the furthest since the monitor's inception is remote sensing, which the authors cull from satellite data. In the early years of satellites, there wasn't enough data to build a clear long-term picture of normal or abnormal climates. But little by little, those pictures are coming into a more precise focus.

"Some of these satellites are now coming on 25, 30, 35 years of information being collected; we can start putting that together," Fuchs said.

Most of all, it's given scientists the opportunity to practice on an actual scenario.

"It doesn't hurt, too, that in the last 10 years there's been a very active drought period in the United States," he said. "We've seen droughts over almost every area of the country, and some of them have been significant."